Electrical heating device



p 9, w. w. HICKS 1,927,035

ELECTRICAL HEATING DEVICE Filed July 2, 1928 F I E '.l

FIE| E [DUE] EIUEIIEIDEIDEEIE] III mmcmclcmjnm El DECIDE] ElDEBQEHMEEIUEI El [JEIIUEIDEHDEIEI El [118535511355 I] DEIIDEIEIEJEUU Jr"'Il= E A TTOR E YS Paten ted Sept. 19, 1933 ELECTRICAL HEATING DEVICEWilliam Wesley Hicks, San Francisco, Calif., assignor to Wesix NationalCompany, San Francisco, Calif., a corporation of Delaware ApplicationJuly 2, 1928. Serial No. 289,709

2 Claims. (01. 219-46) This invention relates generally to devices forconverting electrical energy into heat.

It is an object of this invention to devise a novel unit or electricalheating element which can be universally applied to supply heat eitherby conduction or convection.

It is a further object of this invention to devise an electrical heatingunit which is inher- .ently flexible and which can be looped upon itself or which can be bent to various forms without permanentdeformation.

It is a further object of this invention to devise a heating unit havinga relatively small heat lag and a relatively eflicient heat transmittingsurface. 3

Further objects of the invention -will appear from the followingdescription in which I have set forth the preferred embodiment of myinvention. It is to be understood that the appended claims are to beaccorded a range of equivalents consistent with the state of the priorart.

Referring-to the drawing: w Figure 1 is a side elevational view of adevice incorporating my invention.

Fig. 2 is an enlarged cross sectional detail of a portion of the unitshown in Fig. 1.

. Fig. 3 is a detail perspective view showing the metal strip employedfor formingmy flexible metalsheath.

Fig. 4 is a front'elevational view of an electrical air heaterincorporating a unitsuch as shown in Fig..-1."

Fig. 5'is a cross sectionalv view taken along the line 5-5 of Fig. 4.

Fig. 6 is a front elevational view showing an-' other manner in whichdevice of Fig. 1 can be looped about supporting means.

Fig.7 is a detail of a modified form of the unit in which a singlesheathencloses a pair of resist- I -ance conductors.

' fi' elo'ngated 'metal tube. In adapting such-heating units to variousconditions of operation or to different heating appliances with whichthey are employed, they can be bent from the normal shape in which theyare manufactured, but such bending effects a permanent deformation. In

other words a small amount'of bending of the metal sheath or tubeexceeds the elastic limit of the metal with the result that the bend ispermanent. It is apparent that bending of an ele- -ment of this kindmust not only be done carefully beads 12 of insulating material.

so as not to injure the element, but "in most cases the elements cannotagain be straightened or bent to a different shape to suit otherconditions. Furthermore this bending cannot be accomplished quickly andreadily as with the invention herein disclosed. j

' In my invention I enclose an insulated resist.- ance conductor in ametal sheath but this sheath is constructed in such a manner as to beinherently flexible'to such a degree that the elements can be loopedupon itself without permanent deformation.

Referring to the drawing for a detailed description of the preferredembodiments of my invention, in Figs. 1 and 2 I have shown an electricalheating unit comprising a flexible resistance conductor 11 which ispreferably convoluted so as to provide suflicient resistance and a highdegree of flexibility. Conductor 11 is provided with flexibleinsulation, which in this case is preferably formed by a plurality ofcontiguous tubes or and the bead or tubes are enclosed within aninherently flexible metal case 13. a

As an example of an inherently flexible sheath, I have shown aconstruction utilizing a strip 14 made of metal having relatively highresilience. This strip is formed as shown in Fig. 3 so as to Theconductor provide oppositely extending edges 16 and 1'7 and is wound inthe form of a helicoid or a spiral in such a manner that the projectingedges 16 ,and' 17 are caused to interlock between adjacent looping sucha sheath upon itself the e astic limit a of the metal is not exceededand therefore the 'sheath does not take a permanent deformation.

Another advantage of a sheath of this kind is that it is ofcomparatively light weight compared to a solid tube of equal lateralstrength,v and therefore my unit has small heat lag.

The insulating tubes 12 are preferably of such a length, and havesuflicient clearance between the sheath 13 that they will not be crampedand broken when the sheath is flexed to its radius. For connection withthe ends of conductor 11, I have shown suitable connection blocks 18mounted upon the ends of the flexible sheath 13. As a means for securingthese blocks to the sheath, I have shown each block provided with aportion 19 adapted to project within the cooperating end of sheath 13. Asuitable clamp face and increases the surface of contact between servesto efiectively clamp the sheath to portion 19. A suitable connectionterminal 22 is provided upon block 18, and a lead from conductor 11extends to terminal 22 thru the opening 23.

In Figs. 4 and 5 I have shown one particular use for the units shown inFigs. 1 and 2. In this case the unit forms an electrical heating elementfor an air heater. This heater has been shown conventionally ascomprising an. outer housing 26 having an open front which is covered bya suitable grille or front plate 27. Positioned within the housing 26there is a shell 28 which accommodates a supporting plate 29. A flexibleunit such as that described above and which has been indicated generallyat 31, is looped about the support 29 in any convenient way. When in useconvection currents can flow thru grille 29 into and out of the openfront shell 28, and likewise into the lower and out of the upper portionof housing 26 between the shell 23 and the housing.

It is to be noted that because of -the character of my flexible metallicsheath, the outer surface of this sheath is grooved and thus provides aneffective augmented heat transmitting surface. Such a grooved surface isof particular advantage when my unit is employed for heating fluids suchas air, as it materially increases the radiating surthe sheath andsurrounding fluid medium.

In Fig. 6 another adaptation of my heating unit is shown, in which thisunit 31 is looped about and supported by a plurality of insulating knobs32. While in case of the uses illustrated in Figs. 4, 5 and 6, the uniteffects heating principally by radiation and convection, it is apparentthat it can also be employed for heating by direct conduction, as-forexample the unit can be wrapped about or otherwise placed in heatconducting relationship with a body to be heated.

1,927,036 21 surrounding the end portion of sheath 13,

In Fig. '7 I have shown a flexible sheath 33 similar in construction tothat shown in Figs. 1 and 2, but adaptedto enclose a plurality ofresistance conductors 11. In this case the sheath 33 is fiattened andencloses two conductors 11-and their insulating tubes in side by siderelationship. The properties of a unit constructed in this manner aresimilar to the properties of the single conductor unit previouslydescribed.

I claim:

1. In an electrical heating device, a flexible.

resistance conductor, a plurality of insulating tubes strung upon theconductor, a second conprising a spirally wound strip 01 metal havinginterlocking turns, whereby said sheath is capable oi. assuming variouscurved. contours without permanent deformation, the insulating materialof which said tubes are composed being relatively compact, and havingrelatively small heat lag, thereby affording eflicient'heat transferfrom said conductor to said flexible sheath in any position which thesheath may assume, each 01 said tubes being of a length at least equalto but less than twice the width 01' said strip.

WILLIAM WESLEY HICKS.

